Stabilization of nitrocellulose



Patented May 31, 1949 UNITED STATES 2,471,583 STABILIZATION OF NITROCELLULOSE Richard E. Reeves, New Orleans, La., and Joel E. Giddens, Washington, Ga., assignors to the United States of America as represented by the Secretary of Agriculture No Drawing. Application May 16, 1946, Serial No. 670,086

3 Claims.

(Granted under the act of amended April 30, 1928;

This application is made under the act of March 3, 1883, as amended by the act of April 30, 1928, and the invention herein described, if patented, may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment to us of any royalty thereon.

This application is a continuation in part of our copending application for patent, Serial No. 534,370, filed May 5, 1944, granted as Patent No. 2,404,887.

This invention relates to nitrated cellulose, and has for its primary objects an improvement in the process of stabilizing such cellulose, and such other objects as will be apparent in consideration of the following specification:

Due to the use of sulfuric acid in the preparation of nitrocellulose, it is ordinarily necessary to remove the retained sulfate to stabilize the product. This is conventionally accomplished by repeated boiling in water and beating treatments, :2. long and tedious process. It is also known that addition of a little ammonia to the boiling water aids in stabilization. However, in this event it is necessary to control the amount of ammonia added very closely, as the addition of ammonia little beyond slight alkalinity deleteriously affects the nitrocellulose.

According to the invention described and claimed in Patent No. 2,404,887, ammonia is used at a lower temperature, preferably room temperature, as one treatment, in which event the alkalinity need not be so carefully controlled. According to the invention claimed herein, ammonium salts are used instead of the hydroxide, the treating solution being buffered to remain slightly acidic. In this event excess salt can be used with a hot solution with no deleterious effect on the nitrocellulose, and thus be introduced in connection with a boiling treatment. 40

25 out added ammonium sulfate.

March 3, 1883, as 370 0. G. 757) Ammonium salts which yield ammonium ions in the aqueous solution may be used. Ammonium sulfate is preferred, although such salts as ammonium chloride and ammonium carbonate appear to be equally effective.

The following examples exhibit the invention in greater detail:

EXAMPLE I 20 lulose was filtered and drowned in cold tap water.

The nitrocellulose thus prepared was rinsed free of superficial nitrating acids and divided into portions which were subjected to boiling for one hour in various buffered solutions with or with- The composition of the solutions, the amount of added ammonium sulfate, the pH at the beginning and end of the boiling treatment and the stability of the treated samples are indicated in Table 1, the 110 test 30 described in the above-mentioned patent being used. In the table, the pHs of portions 1 and 2 were adjusted with acetic acid, of portions 3 and 4 with citric acid, of portions 5, 6, 7, 8 and 9 with sodium hydroxide, and of portions 10 and 11 with hydrochloric acid. Inspection of this table shows that when the bufiered solutions were employed without added ammonium sulfate, very poor stability was obtained. With ammonium sulfate added to the buffered solutions, excellent stability was obtained in the pH range of 4.0 to 5.5.

Table 1 O Cellulose nitrate boiled Ammonium PH at 25 St Portion one hour with the followsulfate 8,, E

in; 1% solutions, rinsed, added Be and dried g./100 ml i End 1 Sodium acetate- N one 5. 5 5. 5 3 2 d0 0.10 5. 5 5.4 50 3 Potassium citrate- None 5. 5 5. 5 3 4 d0 0.10 5.5 5.4 40 5- Potassium acid phthalata- None 5. 5 5. 4 3 d 0. 5. 5 5. 5 35, 28 O. 10 5. 0 5. 0 28, 36 0.10 4. 5 4. 5 32, 0.10 4.0 4.0 21, 18 0. 10 3. 5 3. 18 0.10 3. 0 3.07 10 observed-even in 82 days, illustrating EXAMPLE II Although the stabilization of nitrocellulose with faintly acid solutions containing ammonium salts is greatly accelerated at elevated temperatures, the following example exhibits a similar efiect on allowing the solutions to act for longer periods of time at ordinary temperatures. Nitrocellulose prepared as in Example I was given a one-hour boil in distilled water, rinsed and placed in a solution containing approximately 0.5 percent ammonium acetate buffered to an initial pH of 5.0. Samples were Withdrawn, after various intervals of time, rinsed and dried. In Table 2, item 1, is shown the duration of the treatment and the 110 stability which was produced in the sample. It is apparent that under these conditions good stability was realized in approximately 24 hours. Also shown in Table 2, item 2, are the results of asim'ilar experiment employing 0.5 percent sodium acetate buffered at an initial pH of 510. TIn this instance, no improved stability was that the ammonium cannot be replaced by sodium ions.

Table 2 Duration of treat- Lltem ment Reagent l min 1 Ammonium acetate...

1 Sodium acetate 82 days Having thus described the invention, what is claimed is: 1

1. The process of stabilizing nitrocellulose comprising boiling nitrocellulose with an aqueous solution containing an ammonium salt which yields ammonium ions in the solution, said solution being buffered to maintain a pH of about 4 to 5.5.

2. The process of stabilizing nitrocellulose comprising boiling nitrocellulose with an aqueous solution containing ammonium sulfate, said solution being buffered to maintain a pH of about 4 to 5.5.

3. The process of stabilizing nitrocellulose comprising treating nitrocellulose With an acid aqueous solution containing an ammonium salt which yields ammonium ions in the solution, said solution being buffered to maintain a pH higher than 4.

RICHARD EREEVES. JOEL E. GIDDENS'.

REFERENCES CITED The following references'are o'f recordin -the file of this patent;

UNITED STATES PATENTS Number Name 'Date 1,633,292 Shipley Jun." 21, 192'7 1,873,061 Snelling'etal Aug. 2-3,'i1932 1,912,399 Norton ...Jun'e6,1933 1,995,117 Eskew Mar. 19,1935 

